The large amounts of data on skeletal muscle metabolism published during the last 15 years contrasts markedly with the limited amount of information on smooth muscle metabolism published over this same period. We have been able to collect, quick-freeze, and store (minus 200 degrees Centigrade) uterine smooth muscle samples from about 20 naturally cycling macaques and 20 monkeys spayed for at least 6 months and treated with estradiol-17 Beta (E2) for 14 days, or with E2 for 14 days and then for 5 to 14 additional days with E2 plus progesterone (P). Plasma levels of E2 and P are determined at the time of biopsy (radioimmunoassay) and the levels are paired in the spayed monkeys treated with hormones and the naturally cycling monkeys. Our current plan is to compare basal activity Kinetics, and hormone (i.e., oxytocin, epinephrine, etc.) sensitivity of the enzymes involved in the synthesis (adenylate and guanylate cyclase) and degradation (cAMP- and cGMP-phosphodiesterase) of the cyclic nucleotides during the follicular and luteal phases of induced and natural menstrual cycles. We have already found that in myometrium cAMP- and cGMP-phosphodiesterase and guanylate cyclase activities are greater in the follicular compared to the luteal phase. We now plan to study adenylate cyclase, cAMP-dependent protein kinase (types I and II), and cGMP-dependent protein kinase activities. The overall activity of prostaglandin (PG) synthetase in the follicular and luteal phases will also be compared, as will the distributions of the various PGs produced i.e., PGE2, PGD2, PGF2 alpha, PGI2, and thromboxane B2. Levels of enzyme activity will be measured in samples of taenia coli to determine if the changes seen during the menstrual cycle are specific for myometrial smooth muscle. Plasma E2 and P levels in these animals will be correlated with changes in metabolism.